DE 43 30 613 A1 discloses a method and an appliance for operating a gas turbine. The gas turbine has a turbine part through which a driving gas flows, while expanding and delivering mechanical work. A fuel, which is burnt in the turbine part, is supplied to the driving gas. The fuel for combustion in the turbine part is admixed to a cooling air flow which is to be supplied to this turbine part. The proportion of the fuel in the cooling air flow is dimensioned in such a way that any self-ignition of the mixture is excluded.
WO 97/29274 shows a method for expanding a combustion gas flow in a turbine and also shows a corresponding turbine. A thermally highly stressed component of the turbine is cooled by means of an associated cooling gas flow, which flows through the component and is supplied from this component to the combustion gas flow. Fuel is additionally metered to the combustion gas flow in the turbine in such a way that compensation is provided for a temperature reduction in the combustion gas flow is compensated by combustion of the additionally metered fuel. The temperature reduction is the result of the cooling gas flow being supplied without fuel being metered to it. The power of the turbine is increased by the additional combustion of fuel without the temperature of the combustion gas having to rise at inlet to the turbine.
For similar turbine design and for similar selection of the materials used in its construction, the useful work delivered by a gas turbine, to which the turbine belongs, is therefore substantially increased. This also avoids the combustion gas flow being further cooled beyond the temperature reduction specified by the expansion. This improves the thermodynamic efficiency of the turbine.
That condition which would be present without the provision of cooling gas flows is essentially produced in the turbine by the additional combustion of fuel. In the case where the cooling gas flow consists essentially of air, the fuel is admixed to a proportion by weight of a maximum of 2% of the cooling gas flow. With this mixing ratio, an unintentional ignition of the mixture of air and fuel is essentially excluded, in particular when the fuel is homogeneously mixed into the cooling gas flow.